<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    .wrapper {
      width: 50vw;
      height: 100vh;
      background-color: grey;

      /* 居中 */
      position: absolute;
      left: 50%;
      transform: translateX(-50%);

      display: grid;
      
      

    }
    .left {
      width: 200px;
      background-color: red;

    }
    .right {
      background-color: green;
      
      flex: 1;
    }
  </style>
</head>
<body>
  <section class="wrapper">
    <section class="left">left right right right right right right right right right right right right</section>
    <section class="right"> right right right right right right right right right right right right</section>
  </section>
</body>
</html>